Thread-carrying looptaker for chain stitch sewing machines with thread catcher and clamping device

ABSTRACT

A combined thread-carrying looptaker and cutting device for chain stitch sewing machines including a thread catcher is fitted with means to clamp, during initiation of a sewing operation, the free cut length of the thread comprising a spring-loaded clamping plate rotatively mounted upon the looptaker body about a pivot axis spaced from and parallel to the axis of a guide bore in the looptaker through which is passed the looptaker thread. The clamping plate has a further guide bore normally registering with the guide bore in the looptaker body and is deflected from its normal position by an abutment thereof camming with the edge of a thread catcher during the latter&#39;&#39;s displacement from its rest position to the thread-cutting position, resulting in clamping of the thread between the plate and looptaker body. The pull on the thread upon formation of the initial stitches of a subsequent sewing operation causes the automatic return of the clamping plate to its normal operating position.

United States Patent [54] THREAD-CARRYING LOOPTAKER FOR CHAIN STITCHSEWING MACHINES WITH THREAD CATCHER AND CLAMPING DEVICE 7 Claims, 3Drawing Figs.

[52] U.S. Cl 1 12/252, 1 12/253 [51] Int. Cl D05b 65/00 [50] Field ofSearch 112/252, 253

[56] References Cited UNITED STATES PATENTS 3,371,633 3/1968 Hedegaard.1. 112/252 3,354,852 11/1967 Kennedyetal.... 3,532,065 9/1968 MarforioPrimary Examiner.lames R. Boler AttorneyGreene & Durr ABSTRACT: Acombined thread-carrying looptaker and 1 upon the looptaker body about apivot axis spaced from and parallel to the axis of a guide bore in thelooptaker through which is passed the looptaker thread. The clampingplate has a further guide bore normally registering with the guide borein the looptaker body and is deflected from its normal position by anabutment thereof camming with the edge of a thread catcher during thelatters displacement from its rest position to the thread-cuttingposition, resulting in clamping of the thread between the plate andlooptaker body. The pull on the thread upon formation of the initialstitches of a subsequent sewing operation causes the automatic return ofthe clamping plate to its normal operating position.

PATENTED AUG] 7 Ian Fig.3

Fig.2

INVENTOR EU rE V Ali/4'55 mael- B477! 4 r/OA'NEY THREAD-CARRYINGLQOPTAKER FOR CHAIN STITCH SEWING MACHINES WITH THREAD CATCHER ANDCLAMPING DEVICE I The present invention relates to double chain stitchsewing machines, more particularly of the type including athreadcarrying oscillating looptaker, a thread catcher to seize thelooptaker threadat the end of a sewing operatiomto draw out the threadto a length sufficient for the sewing of the starting stitches during asubsequent sewing operation, and operate the thread into engagement witha thread-cutting knife, and a clamping ,device to'lock the free cutlength of the thread during formation of the starting stitches.

ln order to prevent the looptaker thread, drawn out prior to cutting bythe thread catcher of a conventional thread cutting device to a lengthsufficient to enable formation of the next starting stitches, from beingwithdrawn from the thread guide of the looptaker by the action of thethread takeup withdrawing definite lengths of thread from the supplyspool required for stitch formation, and furthermore, in order to ensurea safe initiation of the starting stitches, it has already become knownto clamp the end of the thread portion emerging from the egress guidebore of the looptaker between the thread catcher of the cutting deviceand a stationary abutment disposed upon the frame of the sewing machineand exteriorly of the stitchforming tools, until such time as to ensurea safe formation of the starting stitches and to subsequently return thethread catcher to its inoperative or rest position, to thereby releasethe looptaker thread. A relatively complex operating and controlmechanism for the thread catcher is required in a thread: clampingdevice of this type.

According to another proposal, a clamping spring for the free end of thelooptaker thread is disposed in the space underneath the stitching plateand within the operating path of the thread catcher of the cuttingdevice, to clamp the free end ofthe thread, cut after been drawn out toa sufficient length by the thread catcher plate," between saidclampingspring and stitching plate. A drawback of such a thread clampingarrangement is the fact that the clamping force produced by the springvaries widely for threads of different diameters and that adaptation ofthe clamping pressure to the thread diameter is extremely difficult toachieve in practice for the reasons, among others, that the clampingpressure must have a sufficient value to enable the thread takeup towithdraw thread from the supply spool without withdrawing the free endof the thread from the clamp, on the one hand, and that a'substantialpull on the thread is required during the work feed or advance stroke towithdraw the thread from the clamp, on the other handl Among otherdrawbacks, this may result in a contraction of the fabric near the startof a seam, especially during sewing of relatively thin and lightmaterials, due to the locking of the free end of the thread by the clampand lack of sufficient loose thread for the sewing of the startingstitches of the seam, as well as due to the action on the thread by thethread takeup.

Accordingly, an important object of the present invention is theprovision of a looptaker thread-clamping device for chain stitch sewingmachines of the referred to type which, while being of relatively simpleconstruction, is substantially devoid of the foregoing and relateddefects and drawbacks.

A more specific object of the invention is the provision of a,threadclamp of this type which is closed by the thread catcher ofacutting-device and opened automatically after the sewing of thestarting stitches of the new seam.

I The invention, both as to the foregoing and ancillary objects as wellas novel aspects thereof, will be better understood from the followingdetailed description, taken in conjunction with the accompanying drawingforming part of this disclosure and in which: 1

FIG, 1 is a perspective view of a conventional thread-carrying chainstitch looptaker and thread catcher, embodying an automaticthread-clamping device constructed in accordance with the principles ofthe invention;

seizure of the looptaker thread and of its camming edge in initialengagement with said clamping plate; and

FIG. 3, being similar to FIG. 2, shows the device in the clampingposition at the end of the forward operating stroke of the threadcatcher.

Like reference numerals denote like parts in the different views of thedrawing.

With the foregoing objects in view, the invention, according to oneaspect, involves generally the provision of a springloaded clampingplate rotatively mounted upon the looptaker body between a normal and aclamping position, with the pivot axis of said plate being parallel toand spaced a sufficient distance from the axis of the ingress guide boreof the looptaker passing the looptaker thread and with said plate havinga guide bore registering with said ingress guide bore during its normaloperating (sewing) position, in such a manner as to clamp the thread inthe deflected or clamping position of said plate by the resilientpressure between the plate and the adjoining surface of the looptakerbody. Operation of the clamping plate from its normal to its clampingposition is effected by an abutment thereof camming with an edge of thethread catcher of the cutting device during the forward operating strokeof the thread catcher plate towards the cutting position.

The rotatable mounting of the clamping plate upon the looptaker body andrelative positions of the guide bores disposed in said plate and bodyand passing the looptaker thread has the effect that the pull on thethread by the takeup between the supply spool and looptaker and thetension upon the thread after completion of the starting stitches aresubstantially at right angle to the direction of the thread within thedeflecting range between the guide bores, whereby to require arelatively slight deflecting force to automatically return the clampingplate to its normal operating position after formation of a safe numberof starting stitches of a new seam being sewn, due to the substantialleverage effect as a result of the distance between the pivot axis andthread guide bore of the plate.

In order to adapt the clamping device for use with threads of differentmaterials and thread diameter, the clamping pressure upon the plate isadjustable, such as by the provision of a clamping spring and setscrewor the like, in the manner as will become further apparent as thedescription proceeds in reference to the drawing.

The latter shows, by way of example, a thread-carrying chain stitchlooptaker comprising an oscillating bar 1, a looptaker foot 2 extendingtransversely from said bar and a neck or support 3 extending from saidfoot substantially parallel to the bar 1 and terminating in the needlethread loop-seizing looptaker beak 4, all of conventional construction.Beak 4 is provided with an egress guide bore 5 near its pointed end anda longitudinal guide groove 6 for passage and guidance in a knownmanner, of the looptaker thread 20 taken from a supply spool (notshown).

During operation, the point of the beak 4 moves along an either straightoscillating path 4a or an elliptical oscillating path 4b, depending onthe type of chain stitch sewing machine, for cooperation, in a knownmanner, with the needle thread (not shown) in the formation of doublechain stitches in the work operated on.

Provided in the neck 3 near the inner end of the beak 4 is an ingressthread guide bore 7 through which is passed the supply limb of thethread 20 supplied by the thread takeup (not shown) which is interposedbetween the supply spool and and the looptaker in accordance with knownsewing machine construction.

Affixed to the underside of the foot 2, by means of a securing screw 9and in accordance with the improvement of the present invention, is abracket or carrier 8 fitted with a pivot pin 10, the axis of which isspaced from and parallel to the axis about the pin 10 is a clampingplate 17 which is provided with a further thread guide bore 1 l,registering with the guide bore 7 in the normal position of the plate,as shown in FIGS. 1 and 2, during operation of the sewing machine. Plate17 is furthermore provided with a slot 12 and has an upper extension 13,forming an abutment 14 for cooperation with the oblique camming edge 15of a thread catcher plate 16 forming part of a conventionalthread-cutting device. The thread catcher l6 functionsin a known mannerby seizing and'drawing out the work limb of the looptaker thread on itsway to the'cutting knife, as indicated by the arrow in the drawing, insuch a manner as to provide a length of free thread upon cuttingsufficient to enable the safe initiation of the starting stitches duringa'subsequent sewing operation.

The clamping plate 17 frictionally engages the outer surface of the neckor support 3 by the action of a flat spring 18 overlying the outersurface of the plate 17 and being secured by the aid of an adjustablesetscrew 19 passing through a bore in the'spring 18 and the slot 12 inthe plate 17, and threadedly engaging'th'e neck 3. The clamping pressurebetween the plate 17 and neck 3 may thus be adjusted, to suit existingoperating conditions and requirements and to define two fixed limitpositions of the clamping plate by the slot 12, viz. an operativeposition of registry of the guide bores 7 and 1 1, FIGS. 1 and 2, and atemporary deflected or clamping position after-cutting of the thread, asshown in FIG. 3.

As previously described,.the looptaker thread is passed, in the mannershown, from the supply spool and via the thread takeup (not shown)through the guide bore 11 of the clamping plate 17, the ingress guidebore 7 of the looptaker neck 3, along the guide groove 6, through theguide bore of the beak 4, and on to the work being operated on. The partof the thread between the bore 5 and the work is ordinarily known as thework limb of the thread to be cutupon completion of the sewingoperationby the thread-cutting device. During operation of the sewingmachine, with the axes of the guide bores 7 and 11 being in registry, asshown in FIGS. 1 and 2, thethread may be drawn freely through thelooptaker, as required for the stitching operation.

In operation, if, upon stoppage, at the end of a seam-sewing operation,of a sewing machine equipped with a clamping device according to theinvention, the thread catcher 16 of the cutting device is displaced,either manually or automatically, in thedirection opposite to the pointof the looptaker beak 4, as indicated by the arrow in FIG. 1, to seizethe work limb of the thread 20 above said beak, to draw out the threadto a length sufficient to ensure the safe formation of starting stitchesduring the next sewing operation, and to operate the threadinto.engagement with a stationary cutting knife (not shown) of knownconstruction, the edge 15 of the thread catcher 16 engages the abutment14 of the clamping plate 17, as shown in FIGS. 1 and 2, whereby todeflect said plate about the pivot to its thread-clamping position, asshown in FIG. 3. In the latter, the thread 20 is clamped between thespringloaded plate 17 and the outer surface of the neck 3. Subsequently,the thread catcher 16 is displaced to its rest or starting position (notshown) in the direction opposite to the arrow, whereby to retain plate17 in the clamping position by the pressure exerted by the spring 18.

During starting of the next sewing operation or cycle, the clampingdevice remains in the closed or clamping position, FIG. 3, until thefree starting length of the thread 20 has become safely interlocked withthe needle thread during the formation of the first chain stitch orstitches of the new seam being sewn. There is ensured thereby that thefree end of the looptaker thread is utilized in its full previouslydrawnout length for the formation of the starting stitches, preventingthereby distortion or tightening of the fabric on the one hand, andwithdrawal of the thread'20 from its guide bores 5, 7 and 11 by theaction of the thread takeup interposed between the clamping point andsupply spool, on the other hand.

After the starting stitches of the new seam have been sewn and the freedrawnout end of the looptaker thread has been fully consumed,continuation of the stitch formation will result in tensioning of thelimb of the thread between the clamping point and the work accompaniedby the simultaneous pull on the thread limb between the clamping pointand thread takeup by the action of the latter. Both forces actsubstantially at right angle to the thread between the guide bores 7 andwith a leverage determined by the distance between the pivot 10 andguide bore 11 of the plate 17, in such a manner as to safely andautomatically deflect or return the latter by a relatively slight forcefrom the clamping position, FIG. 3, to the normal or sewing position,FIG. 2, and to enable the looptaker thread 20 to be withdrawn freelyfrom the supply spool via the thread takeup and thread guide bores 11, 7and 5, during continued sewing operation. The limit operating positionsof the plate 17 (sewing and clamping positions) are determined by theslot 12 in the plate 17, while the clamping pressure may be adjusted bythe aid of the setscrew 19, to suit different types of thread and threaddiameters.

In the foregoing, the invention has been described in reference to aspecific exemplary or illustrative device. It will be evident thatvariations and modifications, as well as the substitution of equivalentparts for those shown, may be made without departing from the broaderspirit and purview of the invention.

I claim:

1. In a chain stitch sewing machine, the combination comprising:

l. a thread-carrying oscillating looptaker including a support having afirst thread guide bore and a looptaker beak extending from saidsupport,

2. a thread catcher forming part of a cutting device and operable from arest position to a cutting position, for the drawing out of thelooptaker thread, and back to said rest position upon cutting of thethread,

3. a spring-urged thread-clamping plate in resilient frictionalengagement with and rotatively mounted upon said support about a pivotaxis spaced from and parallel to the axis of said first guide threadbore, said plate having a second thread guide bore registering with saidfirst guide bore in its inoperative position during operation of thesewing machine, and

4. means to deflect said plate to an operative position by displacementof said thread catcher from said rest position to said cuttingpositions,

5. whereby to relatively displace said first and second guide bores andto clamp said thread between said plate and said support.

2 In a chain stitch sewing machine as claimed in claim 1, wherein saidthread catcher has the form of a plate and said clamping plate has anabutment camming with said thread catcher plate, to deflect saidclamping plate during operation of said thread catcher from its restposition to its cutting posi- Hon.

3. In a chain stitch sewing machine as claimed in claim 1, includingmeans to fix the inoperative and operative positions of said clampingplate.

4. In a chain stitch sewing machine as claimed in claim 1, including anadjustable clamping spring urging said plate against said support.

5. In a chain stitch sewing machine as claimed in claim 1, including aflat spring having a perforation and overlying said clamping plate, anda setscrew passing through said perforation and a slot in said plate andthreadedly engaging said support, for adjusting the clamping pressurebetween said plate and said support and to fix the inoperative andoperative position of said plate by said slot.

6. In a chain stitch sewing machine as claimed in claim 1, includingadjusting means to vary the clamping pressure between said plate andsaid support, to automatically return said plate from its operativeposition to its inoperative position by the pull on the thread aftersewing of a predetermined number of starting stitches.

7. In a chain stitch sewing machine, the combination comprising:

2. a thread catcher plate forming part of a cutting device and operablefrom a rest position to a cutting position, for the drawing out of thelooptaker thread, and back to said rest position upon cutting of thethread,

3. a spring-urged thread-clamping plate in resilient frictionalengagement with and rotatively mounted upon said support about a pivotaxis spaced from and parallel to the axis of said first guide bore, saidclamping plate having a third guide bore registering with said firstguide bore in its inoperative position during operation of the sewingmachine,

. means to deflect said clamping plate to an operative position bycamming with said thread catcher plate during displacement of the latterfrom its rest position to its cutting position,

. whereby to relatively displace said first and third guide bores and toclamp said thread between said clamping plate and said support,

. the pressure between said clamping plate and said support being suchas to cause an automatic return of said plate from its operativeposition to its inoperative position by the pull on the thread aftersewing of the predetermined number of starting stitches.

1. In a chain stitch sewing machine, the combination comprising:
 1. athread-carrying oscillating looptaker including a support having a firstthread guide bore and a looptaker beak extending from said support,
 2. athread catcher forming part of a cutting device and operable from a restposition to a cutting position, for the drawing out of the looptakerthread, and back to said rest position upon cutting of the thread,
 3. aspring-urged thread-clamping plate in resilienT frictional engagementwith and rotatively mounted upon said support about a pivot axis spacedfrom and parallel to the axis of said first guide thread bore, saidplate having a second thread guide bore registering with said firstguide bore in its inoperative position during operation of the sewingmachine, and
 4. means to deflect said plate to an operative position bydisplacement of said thread catcher from said rest position to saidcutting positions,
 5. whereby to relatively displace said first andsecond guide bores and to clamp said thread between said plate and saidsupport.
 2. a thread catcher forming part of a cutting device andoperable from a rest position to a cutting position, for the drawing outof the looptaker thread, and back to said rest position upon cutting ofthe thread,
 2. In a chain stitch sewing machine as claimed in claim 1,wherein said thread catcher has the form of a plate and said clampingplate has an abutment camming with said thread catcher plate, to deflectsaid clamping plate during operation of said thread catcher from itsrest position to its cutting position.
 2. a thread catcher plate formingpart of a cutting device and operable from a rest position to a cuttingposition, for the drawing out of the looptaker thread, and back to saidrest position upon cutting of the thread,
 3. a spring-urgedthread-clamping plate in resilient frictional engagement with androtatively mounted upon said support about a pivot axis spaced from andparallel to the axis of said first guide bore, said clamping platehaving a third guide bore registering with said first guide bore in itsinoperative position during operation of the sewing machine,
 3. In achain stitch sewing machine as claimed in claim 1, including means tofix the inoperative and operative positions of said clamping plate.
 3. aspring-urged thread-clamping plate in resilienT frictional engagementwith and rotatively mounted upon said support about a pivot axis spacedfrom and parallel to the axis of said first guide thread bore, saidplate having a second thread guide bore registering with said firstguide bore in its inoperative position during operation of the sewingmachine, and
 4. means to deflect said plate to an operative position bydisplacement of said thread catcher from said rest position to saidcutting positions,
 4. In a chain stitch sewing machine as claimed inclaim 1, including an adjustable clamping spring urging said plateagainst said support.
 4. means to deflect said clamping plate to anoperative position by camming with said thread catcher plate duringdisplacement of the latter from its rest position to its cuttingposition,
 5. whereby to relatively displace said first and third guidebores and to clamp said thread between said clamping plate and saidsupport,
 5. In a chain stitch sewing machine as claimed in claim 1,including a flat spring having a perforation and overlying said clampingplate, and a setscrew passing through said perforation and a slot insaid plate and threadedly engaging said support, for adjusting theclamping pressure between said plate and said support and to fix theinoperative and operative position of said plate by said slot. 5.whereby to relatively displace said first and second guide bores and toclamp said thread between said plate and said support.
 6. In a chainstitch sewing machine as claimed in claim 1, including adjusting meansto vary the clamping pressure between said plate and said support, toautomatically return said plate from its operative position to itsinoperative position by the pull on the thread after sewing of apredetermined number of starting stitches.
 6. the pressure between saidclamping plate and said support being such as to cause an automaticreturn of said plate from its operative position to its inoperativeposition by the pull on the thread after sewing of the predeterminednumber of starting stitches.
 7. In a chain stitch sewing machine, thecombination comprising: